1 files changed, 188 insertions, 0 deletions
diff --git a/xpcom/ds/nsInterfaceHashtable.h b/xpcom/ds/nsInterfaceHashtable.h
new file mode 100644
index 0000000000..9c9378e8a0
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+++ b/xpcom/ds/nsInterfaceHashtable.h
@@ -0,0 +1,188 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsInterfaceHashtable_h__
+#define nsInterfaceHashtable_h__
+
+#include "nsBaseHashtable.h"
+#include "nsHashKeys.h"
+#include "nsCOMPtr.h"
+
+/**
+ * templated hashtable class maps keys to interface pointers.
+ * See nsBaseHashtable for complete declaration.
+ * @param KeyClass a wrapper-class for the hashtable key, see nsHashKeys.h
+ *   for a complete specification.
+ * @param Interface the interface-type being wrapped
+ * @see nsDataHashtable, nsClassHashtable
+ */
+template <class KeyClass, class Interface>
+class nsInterfaceHashtable
+    : public nsBaseHashtable<KeyClass, nsCOMPtr<Interface>, Interface*> {
+ public:
+  typedef typename KeyClass::KeyType KeyType;
+  typedef Interface* UserDataType;
+  typedef nsBaseHashtable<KeyClass, nsCOMPtr<Interface>, Interface*> base_type;
+
+  nsInterfaceHashtable() = default;
+  explicit nsInterfaceHashtable(uint32_t aInitLength)
+      : nsBaseHashtable<KeyClass, nsCOMPtr<Interface>, Interface*>(
+            aInitLength) {}
+
+  /**
+   * @copydoc nsBaseHashtable::Get
+   * @param aData This is an XPCOM getter, so aData is already_addrefed.
+   *   If the key doesn't exist, aData will be set to nullptr.
+   */
+  bool Get(KeyType aKey, UserDataType* aData) const;
+
+  /**
+   * @copydoc nsBaseHashtable::Get
+   */
+  already_AddRefed<Interface> Get(KeyType aKey) const;
+
+  /**
+   * Gets a weak reference to the hashtable entry.
+   * @param aFound If not nullptr, will be set to true if the entry is found,
+   *               to false otherwise.
+   * @return The entry, or nullptr if not found. Do not release this pointer!
+   */
+  Interface* GetWeak(KeyType aKey, bool* aFound = nullptr) const;
+
+  /**
+   * Allows inserting a value into the hashtable, moving its owning reference
+   * count into the hashtable, avoiding an AddRef.
+   */
+  void Put(KeyType aKey, already_AddRefed<Interface>&& aData) {
+    if (!Put(aKey, std::move(aData), mozilla::fallible)) {
+      NS_ABORT_OOM(this->mTable.EntrySize() * this->mTable.EntryCount());
+    }
+  }
+
+  [[nodiscard]] bool Put(KeyType aKey, already_AddRefed<Interface>&& aData,
+                         const mozilla::fallible_t&);
+  using base_type::Put;
+
+  /**
+   * Remove the entry associated with aKey (if any), optionally _moving_ its
+   * current value into *aData, thereby avoiding calls to AddRef and Release.
+   * Return true if found.
+   * @param aKey the key to remove from the hashtable
+   * @param aData where to move the value (if non-null).  If an entry is not
+   *              found it will be set to nullptr.
+   * @return true if an entry for aKey was found (and removed)
+   */
+  inline bool Remove(KeyType aKey, Interface** aData = nullptr);
+};
+
+template <typename K, typename T>
+inline void ImplCycleCollectionUnlink(nsInterfaceHashtable<K, T>& aField) {
+  aField.Clear();
+}
+
+template <typename K, typename T>
+inline void ImplCycleCollectionTraverse(
+    nsCycleCollectionTraversalCallback& aCallback,
+    const nsInterfaceHashtable<K, T>& aField, const char* aName,
+    uint32_t aFlags = 0) {
+  for (auto iter = aField.ConstIter(); !iter.Done(); iter.Next()) {
+    CycleCollectionNoteChild(aCallback, iter.UserData(), aName, aFlags);
+  }
+}
+
+//
+// nsInterfaceHashtable definitions
+//
+
+template <class KeyClass, class Interface>
+bool nsInterfaceHashtable<KeyClass, Interface>::Get(
+    KeyType aKey, UserDataType* aInterface) const {
+  typename base_type::EntryType* ent = this->GetEntry(aKey);
+
+  if (ent) {
+    if (aInterface) {
+      *aInterface = ent->GetData();
+
+      NS_IF_ADDREF(*aInterface);
+    }
+
+    return true;
+  }
+
+  // if the key doesn't exist, set *aInterface to null
+  // so that it is a valid XPCOM getter
+  if (aInterface) {
+    *aInterface = nullptr;
+  }
+
+  return false;
+}
+
+template <class KeyClass, class Interface>
+already_AddRefed<Interface> nsInterfaceHashtable<KeyClass, Interface>::Get(
+    KeyType aKey) const {
+  typename base_type::EntryType* ent = this->GetEntry(aKey);
+  if (!ent) {
+    return nullptr;
+  }
+
+  nsCOMPtr<Interface> copy = ent->GetData();
+  return copy.forget();
+}
+
+template <class KeyClass, class Interface>
+Interface* nsInterfaceHashtable<KeyClass, Interface>::GetWeak(
+    KeyType aKey, bool* aFound) const {
+  typename base_type::EntryType* ent = this->GetEntry(aKey);
+
+  if (ent) {
+    if (aFound) {
+      *aFound = true;
+    }
+
+    return ent->GetData();
+  }
+
+  // Key does not exist, return nullptr and set aFound to false
+  if (aFound) {
+    *aFound = false;
+  }
+  return nullptr;
+}
+
+template <class KeyClass, class Interface>
+bool nsInterfaceHashtable<KeyClass, Interface>::Put(
+    KeyType aKey, already_AddRefed<Interface>&& aValue,
+    const mozilla::fallible_t&) {
+  typename base_type::EntryType* ent = this->PutEntry(aKey);
+  if (!ent) {
+    return false;
+  }
+
+  ent->SetData(std::move(aValue));
+  return true;
+}
+
+template <class KeyClass, class Interface>
+bool nsInterfaceHashtable<KeyClass, Interface>::Remove(KeyType aKey,
+                                                       Interface** aData) {
+  typename base_type::EntryType* ent = this->GetEntry(aKey);
+
+  if (ent) {
+    if (aData) {
+      ent->GetModifiableData()->forget(aData);
+    }
+    this->RemoveEntry(ent);
+    return true;
+  }
+
+  if (aData) {
+    *aData = nullptr;
+  }
+  return false;
+}
+
+#endif  // nsInterfaceHashtable_h__